Currently, flash memory has become the mainstream of non-volatile memory. Depending on the structures, the flash memory can be divided into two types: NOR flash memory and NAND flash memory. The main feature of the flash memory is that it can retain long-term storage information without requiring power. The flash memory has many advantages, such as high integration, fast access speed, and easy to erase and rewrite, etc. Therefore, it has a wide range of applications in many fields such as microcomputer, and automatic control, etc.
A contact-hole process is an indispensable process in semiconductor device manufacturing. A contact-hole plug is an important medium to connect to the device active region and the metal layer in the back end, and finally to connect to external circuit. With gradual reduction in feature dimension, the spacing between the devices becomes smaller and smaller, and it is more difficult for processes interconnecting the devices. Therefore, a self-aligned contact-hole etching process (SAC) has been developed, which reduces the process limitations of the lithography station when the feature dimension becomes smaller.
However, such contact-hole plug formed by existing techniques often leads to the decrease in electrical properties and reliability of the semiconductor structure. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.